Radiation crosslinkable polyesters and polyesterethers

ABSTRACT

Solvent-soluble polymeric esters and polymeric esterethers with radiation-crosslinkable ethylenic unsaturation in the linear polymeric structure, and recurring pendant hydroxyl groups, are derived from monomers which include diepoxides and monomers with at least one α,β-unsaturated carboxylic acid group. These polymeric products react with cyclic anhydrides to form aqueous alkaline-soluble polymers which are useful as films for photomechanical processes, including lithographic applications and as photoresists.

BACKGROUND OF THE INVENTION

This invention is directed to photocrosslinkable compositions useful inthe photomechanical arts, e.g., in the manufacture of lithographicprinting plates, printed circuits, and the like.

It is known to prepare photopolymerizable compositions which contain,inter alia, an organic polymer binding material, anaddition-polymerizable ethylenically unsaturated compound, e.g.,vinylidene and vinyl monomers, preferably of the acrylic or alkacrylicester type, and an addition-polymerization initiator which isactivatable by actinic radiation. When one of these compositions isformed into a photopolymerizable layer of uniform thickness and adheredto a suitable base support, the resulting structure is called aphotopolymerizable element. The photopolymerizable layer is then exposedto actinic radiation through a suitable pattern until substantialaddition polymerization takes place in the exposed image areas. Theunexposed portions are removed with a solvent, leaving a relief imageuseful for printing and other applications.

BACKGROUND ART

Photosensitive compositions comprising polymers having pendant cinnamateside chains, e.g., photocrosslinkable polyvinyl cinnamate, are disclosedin "Photoresist: Materials and Process," by W. S. De Forest, McGraw-Hill(175) pages 24-29. Other such polymers having pendant freecarboxyl-containing groups are disclosed in U.S. Pat. No. 3,770,443"Photosensitive Composition Comprising A Photosensitive Polymer" (1973).Other materials useful in this technology are (1) the ethylenicallyunsaturated polyhydroxy diester polyethers disclosed in U.S. Pat. No.3,661,576 "Photopolymerizable Compositions and Articles" (1972); (2)linear polyesters of glycols and cinnamic acids which are substituted inthe para position with --OH, --COOH, or --CH═CH--COOH groups, asdisclosed in British specification Nos. 951,928 and 838,547 and U.S.Pat. No. 3,030,208, and (3) related linearly unsaturated polymers withpendant and linearly substituted aqueous sensitive groups as describedin U.S. Pat. Nos. 3,929,489; 4,073,777 and British Pat. No. 1,470,059.

The photosensitive compositions disclosed in these references sufferfrom various disadvantages, including less than optimum mechanicalproperties in some cases and the need for special, and sometimes highboiling and toxic, coating solvents and developers in others. Anotherdisadvantage is the formation of by-products and the need to remove themduring the polymer synthesis. Photopolymerizable acrylic layers usuallyrequire protective overcoats or cover sheets to exclude oxygen whenexposed to actinic radiation.

The present invention provides a new class of radiation-crosslinkablepolymers which avoid these deficiencies.

SUMMARY OF THE INVENTION

The present invention is based on the discovery of, and the synthesisof, a new class of radiation-sensitive condensation polymers which areuseful as photocrosslinkable elements in lithographic and photoresistapplications. This new class of condensation polymers is composed of (a)linear, film-forming, polyesters and polyesterethers which arehydroxy-substituted, i.e., have a multiplicity of recurring pendanthydroxyl groups, and also have radiation-crosslinkable ##STR1## groupspredominantly linked through recurring ester bonds as part of the linearpolymeric structure, and (b) the dicarboxylic semi-esters (half esters)of the aforesaid polymers, formed by reacting the polymer with a cyclicanhydride to convert some or all of the hydroxyl groups to semi-esters.The hydroxy-containing polymers are derived from the reaction ofdiepoxide monomers, such as the diglycidyl ethers of dihydroxybenzenes,with polyester or polyester-ether-forming difunctional monomers havingat least one --CH═CHCOOH group to provide the ##STR2## repeating unit.The repeating ##STR3## units are preferably formed from cinnamic acidand its derivatives and can be defined by the formula ##STR4## where R₁is --COOH, --CH═CHCOOH, or --OH. Preferably R₁ is --CH═CHCOOH as in thecase of 1,4-phenylene diacrylic acid. This invention also includescoating compositions of the aforesaid linear polymers and theirsemi-esters, as well as articles comprising supports coated therewith.

DETAILED DESCRIPTION OF THE INVENTION

In terms of structural formula, the linear repeating unit making up thepolymeric backbone structure with pendant hydroxyl groups can berepresented by formula I, ##STR5## wherein R₂ is a divalent hydrocarbonunit, e.g., aryl, alkyl, aralkyl, or cycloalkyl having 2-20 carbonatoms, and wherein R₂ may be derived from alicyclic and aliphatic diolsup to C₁₈, but is preferably aryl and preferably derived from dihydricphenols, dihydric naphthols, bisphenols, dihydroxy-biphenyls, ordihydroxynaphthalenes; and wherein R₂ may also be partially or totallysubstituted with a C₁ to C₁₀ alkyl or cycloalkyl, aryl, or halogen; andwherein R₃ is a divalent aryl, aroyl, arylacryloyl, furylacryloyl,pyridylacryloyl, or thienylacryloyl group unit, as described by formulaII below, wherein the aromatic unit for aryl is phenyl, biphenyl, ornaphthyl, and the aromatic unit for aroyl is benzoyl or naphthoyl, andwherein one of the R₃ cyclic carbon atoms is directly attached to theβ-carbon of the α,β-ethylenic ester group of the repeating unit; andwherein the aromatic unit of the R₃ group can be unsubstituted orpartially or totally substituted with a C₁ to C₈ alkyl or cycloalkyl,aryl, aralkyl, or halogen group. ##STR6##

These polyesters and polyesterethers, or the dicarboxylic acidsemi-esters thereof prepared by reacting the pendant hydroxyl groups ofthe hydroxy-substituted polyester or polyesterether with a cyclicanhydride, such as succinic anhydride, can be coated on appropriate filmor metal supports, the resulting coating dried and imagewise exposed toactinic radiation, and then developed in either an organic, an aqueousorganic, or an aqueous alkaline development solution to selectivelyremove unexposed areas.

A special advantage of this invention is that it permits adjustment andcontrol of aqueous sensitivity, as well as other polymer properties,independently from the polymerization synthesis step. Thus,photosensitivity need not be diminished by replacing some of thephotosensitive monomer by nonphotosensitive solubilizing monomer. Thustype of replacement can be done if so desired. Another advantage is theability to provide excellent adhesion directly to a substrate,particularly to metal supports used in lithographic processes.

Still another advantage is the ability to readily and reproducibly makelinear polymers which are solvent-soluble (soluble in conventionalorganic and aqueous-organic solvents), as well as being film-forming,thermally stable, reactive polymers, and to do so without formation ofby-products and without undesirable side reactions which can lead to theformation of insoluble gels and to crosslinked, insoluble solids. Theattainment of this advantage is most unexpected in view of the state ofthe art. It is well known in the art that dicarboxylic acids and phenolsare among the acid curing agents for diepoxides, and that they canparticipate in the reaction to become part of the polymer structure;this is described in Chapters 5 and 11 of the "Handbook of EpoxyResins," H. Lee and K. Neville, McGraw-Hill (1967). More specifically,these authors point out that curing of liquid or thermoplastic epoxidesgenerally converts them to insoluble gels or infusible and insoluble,crosslinked thermoset solids. Several kinds of acid curing reactions canoccur which lead to crosslinking: (1) a hydroxyl group formed from theepoxide can react with epoxy and carboxylic acid groups to bring aboutcrosslinking as described by Lee and Neville and in U.S. Pat. No.2,962,469; (2) etherification between the different epoxy chains canlead to insoluble crosslinked chains. By either mechanism, the resultantinfusible, insoluble cured products are totally unwanted for ourpurposes.

In accordance with the present invention, the use of a basic catalystfor the curing of diepoxides will avoid an undesirable premature thermalcrosslinking reaction; instead it initiates the formation of linear,solvent-soluble, film-forming, thermally stable, and essentiallyuncrosslinked, reactive polymers which can be isolated, characterized,if so desired, and then converted at a later stage to insolublecrosslinked solids by radiation curing. The invention also permits theconversion of a polymer product which is soluble in an organic oraqueous organic solvent to a semi-ester which is soluble in an aqueousalkaline solvent. That conversion is effected using a cyclic anhydride,a reagent commonly used to crosslink and insolubilize epoxy-derivedpolymers, as described in U.S. Pat. No. 2,890,210.

The radiation-sensitive condensation polymers of this invention, and thesemi-ester derivatives thereof, have low oxygen sensitivity, which makesit possible to provide high image quality without the need for overcoatsor cover sheets. Typically and preferably, the polymers are made byreacting a radiation-sensitive dicarboxylic acid like 1,4-phenylenediacrylic acid with a diepoxide, preferably the diglycidyl ether of adihydroxybenzene such as resorcinol, or of a bisphenol like Bisphenol A.

Suitable starting materials for preparing the new class of polymers andthe radiation-sensitive coating compositions containing said polymers,are described in greater detail below.

Acids: Among the α,β-unsaturated carboxylic acids which may be employedare those conveying radiation crosslinkability, e.g., 1,4-, 1,3- and1,2-phenylenediacrylic acid, preferably the 1,4-acid; furyl-, pyridyl-,and thienyldiacrylic acids; 2-carboxy-, 3-carboxy- and 4-carboxycinnamicacids; also 2-hydroxy-, 3-hydroxy- and -4-hydroxycinnamic acids.Optionally, nonradiation-sensitive dicarboxylic or phenolic-carboxylicacids like succinic, terephthalic, and hydroxybenzoic acids can be usedto replace some of the radiation-sensitive acids in order to conveycertain desirable mechanical and physical properties, e.g., adhesion andsolubility.

Diepoxides: Compounds of this class which are most useful in theinvention include the diglycidyl ethers derived from dihydric phenolslike hydroquinone, catechol, resorcinol (which is preferred),dihydroxybiphenyls, dihydroxynaphthalenes, bisphenols, includingBisphenol A, a preferred compound, and, for improved flame resistance,its tetrachloro- and tetrabromo-derivatives. Diglycidyl ethers derivedfrom aliphatic and alicyclic diols, although less preferred, areespecially useful as optional reagents to modify such properties asflexibility and softening temperature. Examples of these diols includesimple ones like 1,6-hexanediol and 1,4-bis(hydroxymethyl)cyclohexane,and more complex ones like 1,3-bis(3-hydroxypropyl)tetramethyldisiloxaneand 2,5-bis(hydroxymethyl)tetrahydrofuran. Other useful diepoxidesinclude the glycidyl esters of aliphatic diacids, and of polyethyleneglycols.

In addition to the diglycidyl ethers, other diepoxides may be used asdisclosed, for example, in U.S. Pat. Nos. 2,750,395, 2,890,194, and3,173,971. Both these and the aforementioned diglycidyl ethers may beused, singly or in combination, in accord with the particularly desiredproperties sought for the polymers. Most of these compounds areavailable commercially as raw materials for epoxy-type resins oradhesives. Some more common examples of these are the Epons® from ShellChemical Co.; the DER® epoxy resins from the Dow Chemical Co; certainBakelite® and Unox® resins from Union Carbide Plastics Division andAraldites® from Ciba-Geigy; also certain Epi-Rez® resins fromJones-Dabney (Celanese Corp.) and the Epotuf® resins from ReichholdChemicals, Inc. In general, the lower molecular weight ones arepreferred for the synthesis of more photoactive polyesters.

Basic catalysts: In the reaction between the preferred dicarboxylic acidand the diepoxide, basic catalysts are used, as pointed out above. Theseinclude tertiary amines, e.g., benzyldimethylamine, which is preferred,metal carboxylates, e.g., lithium acetate, quaternary ammoniumhydroxides and halides, and alkali metal hydroxides and alkoxides.

Polymerization solvents: Solvents useful for the polymerization reactioninclude mainly the aprotic polar solvents such asN-methyl-2-pyrrolidone, dimethyl acetamide, sulfolane and the like,which do not have reactive hydroxyl, amino, or other reactive groups.Also, to avoid other unwanted side reactions, it is essential to use ananhydrous solvent which is free of reactive impurities. Somepolymerizations can be done in the absence of a solvent, for example, bymelt polymerization.

Anhydrides: Cyclic anhydrides used to convert the hydroxyl groups to thesemi-ester include saturated and unsaturated aliphatic ones like thepreferred succinic anhydride, octadecyl succinic anhydride,cis-4-cyclohexene-1,2-dicarboxylic anhydride, camphoric anhydride, andmaleic anhydride; aromatic anhydrides such as phthalic anhydride; andsubstituted anhydrides such as 4-methyl-, 3-nitro-, andtetrabromophthalic anhydride; also naphthalic anhydride. Mixedanhydrides like o-sulfobenzoic anhydride are also useful. The amount ofanhydride used will be depend on the desired degree of conversion to thesemi-ester which in turn will depend on the properties desired such asadhesion to the substrate, solubility in aqueous alkali, and dyeability.

Photosensitizers: While the new class of radiation-sensitive polymers ofthis invention is capable of giving useful resist images theirphotosensitivity may be improved, and correspondingly, the requiredexposure decreased by incorporating a suitable sensitizer into thecoating composition. A suitable sensitizer is one which assists thephotocrosslinking. An example of a suitable sensitizer is2-benzoylmethylene-1-methylnaphtho[1,2-d]-thiazoline. Other useful onesare disclosed in U.S. Pat. No. 3,929,489. The selection of sensitizer isbest determined by matching it to the spectral output of the lightsource or vice versa.

Plasticizers: Plasticizers which are useful in the coating compositionsof the invention include β-methoxyethylacetate (methyl Cellosolve®acetate), a preferred compound, dibutylphthalate, andN-ethyltoluenesulfonamide. The choice of plasticizer should be made onthe basis of compatibility with the coating composition, and the desiredproperties of that composition.

Colorants: Fillers, pigments, and dyes (including precursor dyes) can beincluded not only to give a colored or visible image after exposure, orafter exposure and processing, but also to improve physical strength.The amount used will depend on the desired effect. Some useful pigmentsare the phthalocyanines like the Monastral® Blue pigments andparticularly Monastral® Blue GF. Other useful colorants areanthraquinone dyes like Sevron® Blue 2G; triarylmethane dyes likeVictoria Blue B Base; thiazine dyes like methylene blue A ex. conc.;complex dyes like Solvent Red Dye No. 109, a complex of the azo dye C.I.Acid Yellow No. 99 and C.I. Basic Violet No. 10. Photochromic dyes suchas the spirobenzopyrans and leuco dyes, activator combinations such astris(N,N-diethylaminophenyl)methane, and a halogenated activator likecarbon tetrabromide can be used.

Coating solvents: Coating compositions containing the photocrosslinkablepolymers of this invention can be prepared by dispersing or dissolvingthe resin in any suitable solvent or combination of solvents used in theart of preparing polymer dopes. The solvent must be compatible with thesubstrate to be employed. While the choice of solvent will vary with theexact polymer and the coating facilities, preferred solvents include2-ethoxyethanol, 2-(2'-butoxyethoxy)ethanol, N-methylpyrrolidone, andespecially aqueous ammonia with the semi-ester polymers. Other solventsinclude 2-methoxyethanol, dioxane, tetrahydrofuran, dimethylformamideand dimethylacetamide. Optimum concentrations of the crosslinkableresins in the coating solutions are dependent upon the specific resin,the support, and the coating method used. Particularly useful coatingsare obtained when the coating composition contains about 1%-50% byweight, and preferably about 2%-20% by weight, of crosslinkable polymer.Higher concentrations are also useful.

Supports: Suitable supports for the coating compositions of theinvention are metals such as zinc, copper, aluminum, and magnesium;glass; polymeric films, e.g., represented cellulose, cellulose acetate,poly(ethyleneterephthalate), vinyl polymers and copolymers such aspolyalkyl acrylates, polyethylene, etc.; laminated printing circuitboards, cardboard, cloth, parchment, polyethylene and polypropylenecoated paper, and polyamides like nylon. Supports especially useful tomake printing plates, particularly for lithographic printing, includesupports made of anodized aluminum, grained aluminum, copper and zinc.The support can be pretreated, e.g., precoated before applyingradiation-sensitive coating, with known subbing layers such as gelatin,polyacrylamide, and copolymers of vinylidene chloride and acrylicmonomers. The support can also have a filter or anti-halation layer toeliminate unwanted reflection from the support.

The coating composition can be applied to the support by any standardcoating technique, e.g., knife coating, spray coating, extrusioncoating, spin coating. The dry coating should be from about 0.05 to 10microns or greater in thickness. Thicknesses of about 0.1 to 5 micronsare useful for lithographic printing plates. In general, the preferredcoating thickness will depend on various factors, such as the particularuse of the film, and the properties of the polymer used to make thefilm.

Any conventional method of exposure can be used such as exposingimagewise through a transparency or template to a source of actinicradiation, preferably one which is rich in ultra-violet radiation.Suitable sources include carbon arc lamps, mercury vapor lamps,fluorescent lamps, lasers and the like. The exposure time will varydepending on intensity and spectral energy distribution of the source,its distance from the coating, the nature and thickness of the coatingand the degree of crosslinking desired.

The exposed radiation-sensitive elements can be developed by soaking,spraying, swabbing or similarly treating the elements with a developersolution to swell or dissolve and remove only the unexposed areas.Useful developers include the coating solvents described above, e.g.,completely organic solvents like 2-ethoxyethanol and2-(2'-ethoxyethoxy)ethanol; aqueous organic solutions, e.g., 10 volumesof 2-butoxyethanol and 1 volume water or 3 volumes of2-(2'-n-butoxyethoxy)ethanol and 20 volumes of water, are particularlyuseful, as are totally aqueous alkaline solutions, especially for thecarboxylic acid-containing polyesters, the semi-ester derivatives.Alkaline developers from about pH 8 to 14 are useful. The alkalinity canbe controlled by adding water-soluble inorganic compounds such as thealkali metal silicates, bicarbonates, carbonates, and hydroxides.Alkaline soaps are particularly useful as developers to eliminate scumduring processing of lithographic printing plates. Soluble organic basessuch as triethanolamine are also useful, alone or in combination. Thedevelopers may also contain optional additives to give certain effects,e.g., dyes to stain the image or background areas. Surfactants, wettingagents, and hardeners can also be added. Useful wetting agents includesimple polyhydric alcohols such as glycerol and diethylene glycol;esters of inorganic acids such as the phosphate esters of aliphaticalcohols and alkoxy alcohols; commercially available wetting agents like"Zonyl® A," "Triton® X-100," and Tergitol® 15-55.

The invention is illustrated by the following examples.

EXAMPLE 1

To 0.10 g of benzyldimethylamine in a flask fitted with a nitrogen inletset above the reaction surface, a reflux condenser plus drying tube, anda magnetic stirrer, were added in succession, 20 ml of dry,N-methyl-2-pyrrolidone, 4.36 g (0.02 mol) of 1,4-phenylenediacrylicacid, and 4.44 g (0.02 mol) of resorcinol diglycidyl ether. The flaskwas purged with dry nitrogen, and then heated for twenty hours at 110°C. The white reaction slurry dissolved after about an hour, to form acolored solution. This was cooled to room temperature at the end of theheating period; the resulting viscous solution was precipitated as afibrous solid by gradual addition to 0.5% sodium hydroxide solution.This was pulverized in a high speed mixer-blender, filtered, mixed with250 ml distilled water and reworked three times until neutral. Thepolymer can be isolated satisfactorily by precipitation in water insteadof alkali.

The resulting condensation polymer was obtained in 92% yield after airdrying followed by drying over phosphorous pentoxide. Dissolved at 0.5%weight/volume in dimethylformamide, the polymer exhibited an inherentviscosity of 0.23 in a Cannon-Fenske Series 75 viscometer at 30° C. Thispolymer was useful as a photoresist, as demonstrated in the nextExample.

EXAMPLE 2

A filtered coating solution of the following composition:

    ______________________________________                                        Polymer of Example 1    0.10 g                                                2-Benzoylmethylene-1-   0.009 g                                               methylnaptho-[1,2-d]-                                                         thiazoline                                                                    Solvent Red Dye 109     0.009 g                                               2-Methoxyethanol        1.7 ml                                                ______________________________________                                    

was applied to a 3 mil (76 microns) thick polyethylene terephthalatefilm using a doctor knife with a 2 mil (50 micron) slot. The air-driedcoating was exposed through a 2 to 98% halftone 150 line dot target forthree minutes to the radiation of a Sylvania F15T8-BLB light source atan intensity of about 1 mwatt/cm². The exposed film was soaked for 10seconds in an aqueous solution containing 7.4% by weight of2-(2-n-butoxyethyl)ethanol (butyl Carbitol®), rubbed with a cotton swab,and rinsed in water to remove the unexposed areas, leaving hardenedpolymer on the film in the exposed areas.

EXAMPLE 3

The polymerization procedure of Example 1 was repeated through the20-hour/110° C. heating period, then 2.0 g (0.02 mol) of succinicanhydride was added, and the mixture was maintained at 105°-110° C. fortwo hours.

The resulting succinylated polymer was precipitated by adding thesolution at room temperature to 200 ml distilled water with stirring.The filtered solid polymer was washed and dried as in Example 1 to give10.5 g (96%) yield of a cream colored solid, soluble in2-methoxyethanol, tetrahydrofuran, dimethylsulfoxide, dimethylformamide,and N-methyl-2-pyrrolidone. It formed a firm, clear, hard film with goodadhesion to glass. The polymer dissolves in 1% sodium hydroxide and isprecipitated therefrom with hydrochloric acid.

Succinylated polymers prepared following this general procedure includethe following:

    ______________________________________                                                              Theoretical %                                           Diepoxide Employed    Succinylation                                           ______________________________________                                        A Resorcinol diglycidyl ether                                                                       10                                                      B Resorcinol diglycidyl ether                                                                       25                                                      C Resorcinol diglycidyl ether                                                                       50                                                      D Bisphenol A diglycidyl ether                                                                      25                                                      E Bisphenol A diglycidyl ether                                                                      50                                                      ______________________________________                                    

Resorcinol diglycidyl ether, distilled at 128°-131° C./0.10 mm., isavailable as Heloxy® 69 from The Wilmington Chemical Corp. ofWilmington, Del. Bisphenol A diglycidyl ether is available as Epon® 825from The Plastics and Resin Division of The Shell Chemical Co. and as"DER® 332" from the Dow Chemical Company.

Other typical hydroxy and carboxylic acid substituted polymers made byprocedures similar to Examples 1 and 3 are listed in Table 1. Inherentviscosities, IV, were measured as described in Example 1. Glasstransition temperatures, Tg, °C., were measured on a differentialscanning calorimeter, the Du Pont 990 DSC model. This series mainlyshows the effect of catalyst and degree of succinylation on polymerproperties.

                  TABLE 1                                                         ______________________________________                                        mM.   mM.     mM.                  Sol-                                       PDAA  RDGE    BPA    An.    Catalyst                                                                             vent IV  Tg° C.                     ______________________________________                                        20    20      --     --     BDMA   A    0.23                                                                              --                                20    --      20     SA     BDMA   A    0.33                                                                              80                                                     (20 mM)                                                  20    --      20     SA     BDMA   A    0.25                                                                              75                                                     (10 mM)                                                  10    10      --     --     BPA    A    0.24                                                                              70                                10    10      --     --     Pyridine                                                                             A    0.14                                                                              --                                 5     5      --     --     Dabco  A    0.26                                                                              --                                 5    --      5      --     K+ salt                                                                              B    0.24                                                                              76                                                            PDAA                                               5    --      5      --     BDMA   B    0.26                                                                              --                                 5    --      5      --     BDMA   A    0.24                                                                              87                                10    10      --     --     N, NT  A    0.19                                                                              --                                ______________________________________                                         Solvents:                                                                     A = Nmethyl-2-pyrrolidone                                                     B = N,Ndimethylacetamide                                                      Reactants:                                                                    PDAA = 1,4phenylene diacrylic acid                                            RDGE = Resorcinol diglycidyl ether                                            BPA = Bisphenol A diglycidyl ether                                            An = Anhydride                                                                BDMA = Benzyldimethylamine                                                    SA = Succinic anhydride                                                       BTA = Benzytrimethylammonium hydroxide                                        Dabco = 1,4diazabicyclo[2.2.2]octane                                          N,N,T = N,Ntetramethylethylene diamine                                   

EXAMPLE 4

Coating solutions of polymers B, C, and E of Example 3, analogous to thesolution of Example 2, were made up and coated, dried, exposed, anddeveloped as in Example 2 but employing the following developers:

3B 0.6% aqueous sodium silicate (by weight)

3C 0.5% aqueous sodium silicate

3E Water solution of 7.4% 2-(2'-butoxyethoxy)ethanol and 0.3% NaOH

Results were similar to those of Example 2.

EXAMPLE 5

A filtered coating solution made from

    ______________________________________                                        Triethylene glycol diacetate                                                                        0.04 g                                                  2-Benzoylmethylene-1-methyl-                                                                        0.032 g                                                 naphth[1,2-d]thiazoline                                                       Polymer 3C            0.80 g                                                  2-Methoxyethanol      8.0 ml                                                  Solvent Red Dye 109   0.04 g                                                  ______________________________________                                    

was whirl coated on aluminum plates and dried as described in Example 9to give a dry film coating weight of 25.8 mg/dcm². The coated plate wasexposed three minutes through a photographic transparency to radiationfrom a 2 Kw pulsed xenon nuArc® source, soaked 20-30 secs in 0.5% sodiumsilicate solution, rubbed with a cotton swab to remove only theunexposed areas, and rinsed.

A similar plate made with Polymer 3E gave similar results when developedin a solution made from 1 part by weight of a 35% sodium silicatesolution, 60 parts water and 50 parts 2-methoxyethanol.

EXAMPLE 6

To demonstrate polymerization/phthalylation, a phthalylated analog ofone of the products of Example 3 was prepared in a manner identical tothat employed there, except that phthalic anhydride was employed attwice the molar proportion of the other ingredients, instead of usingequimolar proportions of succinic anhydride. To use this polymer(polymer 6) as a photoresist, a solution of the composition:

    ______________________________________                                        Polymer 6               0.10 g                                                Solvent Red Dye 109     0.02 g                                                2-Methoxyethanol        2 mil                                                 ______________________________________                                    

was coated on a glass slide to a dry thickness of 0.3 mils (˜7.6microns). The air-dried film was exposed through a transparency for fourminutes to the radiation source of Example 2. Development intetrahydrofuran for thirty seconds resulted in removal of the unexposedareas, leaving a hardened red image in the exposed areas on the slide.

EXAMPLE 7

To illustrate mixed-acid polymerization/succinylation:

In an apparatus analogous to that of Example 3 a mixture of

    ______________________________________                                        dry benzyldimethyl-  0.05 g                                                   amine                                                                         dry N-methyl-2-pyrroli-                                                                            5 ml                                                     done                                                                          1,4-phenylenedi-     0.872 g (4 mM)                                           acrylic acid                                                                  Terephthalic acid    0.116 g (1 mM)                                           Resorcinol diglycidyl-                                                                             1.110 g (5 mM)                                           ether                                                                         ______________________________________                                    

was heated under nitrogen at 120° C. for 23 hours. The resulting orangesolution was cooled to 105° C. and 0.50 g of succinic anhydride wasadded. The solution was kept at 105° C. for two hours, cooled to roomtemperature, and slowly added with stirring to 400 ml distilled water toprecipitate the polymer. After several water washings, the wet polymer(polymer 7) was pulverized in a blender, filtered, air-dried, and thendried under vacuum at 56° C. In order to prepare a resist, a solution of

    ______________________________________                                        Polymer 7               0.1 g                                                 Solvent Red Dye 109     0.02 g                                                2-Methoxyethanol        2.0 ml                                                ______________________________________                                    

was coated on a glass slide to a dry thickness of 0.3 mil (7.6 microns).The air-dried film was exposed for four minutes through a transparencyto radiation from the source of Example 2. Development for thirtyseconds with tetrahydrofuran removed unexposed areas, leaving a hardenedred image in the exposed areas.

EXAMPLE 8

The polymerization/succinylation used in the preparation of Example 3Ewas repeated at the 10 millimol level, substitutingcyclohexane-1,4-dimethanol diglycidyl ether for bisphenol A diglycidylether, and heating for twenty-two hours at 110° C. during thepolymerization. The diglycidyl ether, distilled at 130°-131° C./0.25 mm,is available as Heloxy® MK107 from the Wilmington Chemical Corp. ofWilmington, Del. The product was a cream-colored polymer (polymer 8). Todemonstrate its use, a coating solution of

    ______________________________________                                        Polymer 8               0.3 g                                                 2-methoxyethanol        2 ml                                                  ammonium hydroxide      0.25 ml                                               (38%)                                                                         ______________________________________                                    

was coated on a glass slide to give a dry film 0.15 mil (3.8 microns)thick. The coated slide was heated five minutes at 60° C., cooled toroom temperature, and exposed for six minutes through a transparency toradiation from the source described in Example 2. Development withaqueous 0.4% sodium silicate solution removed unexposed areas, leavinghardened polymer on the plate in the exposed areas.

EXAMPLE 9

Two well dispersed pigmented mixtures, A and B of Table II, were whirlcoated on silicate-treated anodized aluminum plates and post-dried at130° C. to give dry film coating weights of 25 mg/dcm² and 26 mg/dcm²,respectively.

                  TABLE II                                                        ______________________________________                                        Composition         A          B                                              ______________________________________                                        Polymer 3C          1.60 g     1.40 g                                         Carboset® 525*  --         0.20 g                                         2-Benzoylmethylene-1-methyl                                                                       0.064 g    0.064 g                                        naphth[1,2-d]thiazoline                                                       2-Ethoxyethyl acetate                                                                             0.048 g    0.048 g                                        Monastral® Blue GF                                                                            0.15 g     0.12 g                                         (BT-417D)**                                                                   2-Methoxyethanol    16.0 ml    22.0 ml                                        Tetrahydrofuran     15.0 ml    --                                             Ammoniacal zinc acetate                                                                           0.40 ml    0.040 ml                                       solution                                                                      ______________________________________                                         *Carboset® 525 is an acrylic thermoplastic resin of MW 260,000 and        acid number 76-85 from the B. F. Goodrich Chemical Co., Cleveland, Ohio.      **Monastral® Blue GF is a blue phthalocyanine pigment from E. I. du       Pont de Nemours and Company, Inc., Wilmington, DE.                       

made from 0.50 g zinc acetate dihydrate, 1.5 ml 38% ammonium hydroxideand 50 ml 2-methoxyethanol. The plates were exposed three minutesthrough a standard halftone and line resolution test target to the lightsource of Example 5, swabbed with soaped cotton pads (Ivory soap) toremove only the unexposed areas, and water rinsed. Plates A and B weremounted side by side on a conventional offset lithographic press andafter making 300,000 copies both plates showed good printing of 150 line2% to 98% halftone dots and of the line resolution target. Plate B gavehigher density prints than A.

EXAMPLE 10

A negative working lithographic film was prepared and tested asdescribed by steps A, B, C, and D below.

A. Coating the Photosensitive Layer

A filtered coating solution of the composition:

    ______________________________________                                        Triethyleneglycol diacetate                                                                            0.01 g                                               Polymer 3E               0.80 g                                               2-Benzoylmethylene-1-methyl-                                                                           0.032 g                                              naphth[1,2-d]thiazoline                                                       2-Methoxyethanol         7 ml                                                 Ammoniacal zinc acetate solution                                                                       1.0 ml                                               of Example 9                                                                  ______________________________________                                    

was coated on a 1 mil (25 micron) polyethylene terephthalate film,yielding a 0.1-0.2 mil (2.5-5.0 micron) thick clear dry coating.

B. Coating the Nonphotosensitive Black Layer

A coating dispersion consisting of 10% by weight of a predispersed solidmixture of 55% Carboset® 525 and 45% carbon black and 90% dispersingfluid made from 92% methylene chloride and 8% 2-methoxyethanol wasextrusion-coated to a dry thickness of 0.08 mil (2 micron) onresin-subbed 4 mil (100 micron) polyethylene terephthalate photographicfilm base of the type described in Alles et al., U.S. Pat. No.2,627,088.

C. Laminating Photosensitive Layer to Black Layer

Films A and B were contacted, photosensitive surface to black surface,and passed between moving rolls set at 45 psi, the lower roll heated to˜120° C. After cooling the film to room temperature, the 1 milpolyethylene terephthalate could be peeled off, leaving thephotosensitive layer attached to the carbon-containing layer.

D. Exposure and Development

The element was exposed and processed as in Example 9, except that thedeveloper was a 3% aqueous solution of 9 parts sodium carbonate and 1part sodium bicarbonate. The film as thus prepared and processed, copied2%-98% 150 line halftone dots as high density black images.

EXAMPLE 11

Using the procedure of Example 1 a polyether-ester polymer was made from0.82 g, 5 mM, recrystallized cis/trans p-hydroxycinnamic acid, 1.70 g, 5mM pure bisphenol A diglycidyl ether (Epon® 825), 0.02 gbenzyldimethylamine and 5 ml pure cyclohexanone. The polymer wasprecipitated in petroleum ether and reprecipitated to give 1.0 g whitepowder with an inherent viscosity of 0.21 in dimethylformamide.

A similar polymer made with resorcinol diglycidyl ether formed a clearhard film, soluble in 2-methoxyethanol, which insolubilized when exposedas described for Example 2.

Melt polymerization was used to make a similar polymer by heating anitrogen-blanketed, stirred mixture of 0.06 g benzyldimethylamine, 0.836g 98% pure cis-p-hydroxycinnamic acid, and 1.11 g resorcinol diglycidylether at 72°-75° C. for eight hours. The dry polymer had an inherentviscosity of 0.23 in dimethyl formamide.

EXAMPLE 12

To prepare a composition useful for making a negative workinglithographic film, a filtered solution of 0.040 g of the sensitizer ofExample 2 in 2 ml methylene chloride was added to a high-speed stirredsolution made from

    ______________________________________                                        distilled water      5.0 ml                                                   38% ammonium hydroxide                                                                             0.3 ml                                                   Polymer 3C           1.0 g                                                    1% Triton® X100 in water                                                                       1.0 ml                                                   5% gelatin in water  4.0 g                                                    Ethanol              0.6 ml                                                   ______________________________________                                    

Triton® X-100 is a Rohm and Haas nonionic surfactant,octylphenoxypolyethoxyethanol. A water solution of a fluorocarbonsurfactant, viz. 0.5 ml of 0.2% FC-128 from the Minnesota Mining andManufacturing Co., was added to the coating solution, and the latter wasknife coated on the nonphotosensitive black layer B of Example 10. Theair-dried film was heated in an oven at 130° C. for two minutes to forma 0.1 mil (2.5μ) dry topcoat. The film was exposed for one minute asdescribed for Example 2, soaked for 10 seconds in a 1% aqueous solutionof 9 parts sodium carbonate and 1 part sodium bicarbonate, water-rinsed,and rubbed with a wet cotton swab to remove only the unexposed areas.The exposed areas remained as high density black images.

EXAMPLE 13

A 0.15 mil (2.5 micron) thick dry photoresist was prepared by whirlcoating a filtered solution of

    ______________________________________                                        triethylene glycol diacetate                                                                       0.024 g                                                  sensitizer of Example 2                                                                            0.032 g                                                  Polymer 3C           0.80 g                                                   2-Methoxyethanol     12.0 ml                                                  ______________________________________                                    

on a 1 ml (25 micron) thick copper-clad epoxy board. The film wasexposed as described for Example 2 and processed in 31.5% ferricchloride solution to remove the unexposed film and all of the underlyingcopper. Copper beneath the exposed areas remained firmly attached to theboard. The plate, when rinsed and dried, was useful as a printedcircuit.

I claim:
 1. A class of condensation polymers composed ofradiation-sensitive, film-forming, linear polyesters and polyesterethershaving within the polymeric backbone a multiplicity of repeating unitsof the formula: ##STR7## wherein R₂ is a divalent aryl, alkyl, aralkyl,or cycloalkyl radical having two to twenty carbon atoms, which radicalmay be substituted with a C₁ to C₁₀ alkyl or cycloalkyl, aryl, orhalogen group; and wherein R₃ is a divalent aryl, aroyl, arylacryloyl,furylacryloyl, pyridylacryloyl, or thienylacryloyl group in which thearomatic unit for aryl is phenyl, biphenyl, or naphthyl and wherein oneof the of the R₃ cyclic carbon atoms is directly attached to theβ-carbon of the α,β-ethylenic ester group of the repeating unit, andwherein the aromatic unit of the R₃ group can be substituted with a C₁to C₈ alkyl or cycloalkyl, aryl, aralkyl, or halogen group.
 2. A polymerof claim 1 wherein R₂ is ##STR8## and R₃ is ##STR9##
 3. A dicarboxylicacid semi-ester of a polymer of claim
 1. 4. The polymer of claim 3wherein the semi-ester is an acid succinate or acid phthalate.
 5. Acoating composition comprising a radiation-sensitive polymer of claim 1in a solvent selected from the group consisting of an organic solvent,an aqueous organic solvent, or an aqueous alkaline solvent.
 6. Thecoating composition of claim 5 in admixture with a photosensitizer. 7.The coating composition of claim 6 which additionally contains aplasticizer and a colorant.
 8. The coating composition of claim 7wherein the colorant is a phthalocyanine pigment.
 9. The coatingcomposition of claim 7 wherein the sensitizer is2-benzoylmethylene-1-methylnaphth[1,2-d]thiazoline, the plasticizer ismethylcellosolve acetate, and the colorant is Solvent Red Dye
 109. 10. Acoating composition comprising a radiation-sensitive dicarboxylic acidsemi-ester of a polymer of claim 1 in a solvent selected from the groupconsisting of an organic solvent, an aqueous organic solvent, or anaqueous alkaline solvent.
 11. The coating composition of claim 10 inadmixture with a photosensitizer.
 12. The coating composition of claim11 which additionally contains a plasticizer and a colorant.
 13. Thecoating composition of claim 12 wherein the colorant is a phthalocyaninepigment.
 14. The coating composition of claim 12 wherein the sensitizeris 2-benzoylmethylene-1-methylnaphth[1,2-d]thiazoline, the plasticizeris methylcellosolve acetate, and the colorant is Solvent Red Dye 109.15. A radiation-sensitive element comprising a metal or plastic filmsupport having coated thereon a polymer of claim 1 or a dicarboxylicacid semi-ester of a polymer of claim
 1. 16. The radiation-sensitiveelement of claim 15 wherein the film support is aluminum.
 17. A processfor preparing the photocrosslinkable polyester or polyesterether ofclaim 1, which comprises reacting a diepoxide with a member selectedfrom the class consisting of a phenylene diacrylic acid, furyl-,pyridyl-, and thienyldiacrylic acid, hydroxycinnamic acid, andcarboxycinnamic acid in the presence of a basic catalyst, using ananhydrous solvent.
 18. The process of claim 17 wherein the diepoxide isa diglycidyl ether of a bisphenol or a dihydric phenol.
 19. The processof claim 17 wherein the catalyst is benzyldimethylamine.
 20. The processof claim 17 wherein the phenylene diacrylic acid is1,4-phenylenediacrylic acid.
 21. A process which comprises reacting thephotocrosslinkable polyester or polyesterether formed by the process ofclaim 17 with a cyclic anhydride to form a semi-ester.
 22. A process forpreparing a photosensitive polymer which comprises reacting equimolaramounts of 1,4-phenylenediacrylic acid and resorcinol diglycidyl ether,under anhydrous conditions, in the presence of a basic catalyst,followed by reacting said polyester with succinic anhydride to form asemi-ester.